An industrial robot comprises a manipulator and a control system for controlling the movements of the manipulator. A manipulator is a movable mechanical unit, the movements of which are driven by one or more motors. Traditionally, the control system includes a stationary control device and a handheld control device. The stationary control device comprises a main control unit including a program memory for storing robot programs including movement instructions for the robot, a program executer for executing the movement instructions and a path planner for planning robot paths based on the movement instructions and for generating control signals to drive units of the robot. During operation of the robot, the program instructions are executed, thereby making the robot work as desired. Drive units are controlling the motors of the robot. The control instructions from the main control unit are transformed into control signals for the drive units of the manipulator. The stationary control device is usually connected to an external network (56) as well as a plurality of other equipment.
The patent application US2002188381 discloses such a control system for robots. The disclosed control system comprises a control unit for generating and controlling the robot paths of the manipulator of the robot, a set of drive units generating control signals for controlling motors associated to the moving robot parts of the manipulator, and an Ethernet-type connection for connecting the control unit and the set of drive units.
One disadvantage of this control system is that it is inflexible. If it is desired, for example, to add a new function or replace some part of the control system, it is necessary to intervene and make changes in the existing control system. For instance, the existing control system must either be oversized from the start regarding computer utility and power supply, or the whole of or parts of the control system must be replaced or be rebuilt to obtain the necessary computer utility and power supply.
From the international patent application WO03/103903A1 such a flexible control system is known. The document discloses a control system comprising a plurality of separate modules. The modules are adapted to handle various functions of the control system, such as drive modules adapted to control the motors driving the movements of the manipulator, and a main computer module adapted to execute a robot program with instructions for the movements of the manipulator. Each of the modules has its own power supply and is adapted to communicate with at least one of the other modules, for example via an Ethernet link. The drive modules are either directly connected to the main computer module or connected in series with the first of the drive modules connected to the main computer module.
However this control system has a limited ability of communication, because when connecting a plurality of modules the physical structure of the information transfer system soon becomes complex and demands a large amount of hardware, such as wiring and communication equipment.
An article written by Istvan Bezi and Gabor Tevesz, “Komplett aus standard komponenten eine experimentelle robotsteuerungs architektur”, 20 May 2004 discloses a control system for a robot including a plurality of physically separated modules and an internal network, wherein the modules are arranged as nodes in the internal network and comprises communication means for communicating with the other nodes in the internal network.